1. Field of the Invention
The present invention relates to an optical disk player, and more particularly, to a method for discriminating the type of a disk mounted into an optical disk player.
2. Description of the Related Art
An optical disk player reproduces data recorded on an optical disk, such as a CD (Compact Disk), CD-ROM (Compact Disk-Read Only Memory), LD (Laser Disk), MD (Mini Disk), DVD (Digital Video Disk), etc. Since there are various types of optical disks, the optical disk player should discriminate the type of a disk mounted therein. Especially, a DVD player which uses a CD-series disk as well as a DVD-series disk may not accurately reproduce data unless it determines which type of disk is mounted therein.
Referring to FIG. 1, an optical pickup 102 optically picks up information recorded on a disk and generates an electrically converted RF (radio frequency) signal. The optical pickup 102 has a focusing actuator and a tracking actuator. The focusing actuator is driven by the control of a DSSP (Digital Servo Signal Processor) 114 and shifts an object lens toward an optical axis. The tracking actuator shifts the object lens toward the radial direction of a disk 100 to seek a track. A spindle motor 104 is driven under the control of the DSSP 114 to rotate a disk 100 at a CLV (Constant Linear Velocity). A sled feed motor 106 is driven under the control of the DSSP 114 to move the optical pickup 102.
An RF amplifier 108 amplifies the RF signal received from the optical pickup 102 and shapes a waveform of the amplified RF signal. The RF amplifier 108 supplies a modulation signal during writing to a DSP (Digital Signal Processor) 110 and supplies signals for tracking servo and focusing servo to the DSSP 114. If the disk 100 is a CD-series disk, the modulation signal is an EFM (Eight to Fourteen Modulation) signal. If the disk 100 is a DVD-series disk, the modulation signal is an EFM plus signal. The DSP 110 also restores a BCA (Burst Cutting Area) code reproduced from a BCA code area on the disk 100. An output processor 112 processes the data generated from the DSP 110 and generates a final output signal such as an audio signal. The DSSP 114, controlled by a microcomputer 116, controls tracking servo and focusing servo of the optical pickup 102, sled servo using the sled feed motor 106, and spindle servo, in response to signals received form the RF amplifier 108 and the DSP 110. The microcomputer 116, which is a main controller, controls the overall operation of an optical disk player.
FIG. 2 illustrates a general BCA code structure. The BCA code is comprised of a BCA preamble 200, BCA information data IBCA 202, an error detecting code EDCBCA 204, and error correcting code ECCBCA 206, and a BCA postamble 208. The BCA code is written in the disk together with a corresponding synchronizing byte. That is, the 4-byte BCA preamble 200 is written in the disk together with a BCA synchronizing byte SBBCA. The BCA information data IBCA 202, the error detecting code EDCBCA 204, the error correcting code ECCBCA 206, and the BCA postamble 208 are written in the disk together with a BCA re-synchronizing byte RSBCA.
The BCA information data IBCA 202 (I0–I16n-5) can be expressed by the following equation (1). The error detecting code EDCBCA 204 (ED0–ED3) is a parity for detecting an error of the BCA information data IBCA 202 and is expressed by the following equations (2) and (3) and as the remainder obtained by dividing input data IBCA(x) by a polynomial G(x) which can be expressed by the following equation (4). A bit operation is expressed using a small letter ‘x’.
                                          I            BCA                    ⁡                      (            x            )                          =                              ∑                          i              =              32                                                      128                ⁢                n                            -              1                                ⁢                      bi            ·                          x              i                                                          (        1        )            
                                          EDC            BCA                    ⁡                      (            x            )                          =                              ∑                          i              =              0                        31                    ⁢                      bi            ·                          x              i                                                          (        2        )            EDCBCA(x)=IBCA(x)modG(x)  (3)G(x)=x32+x31+x4+1  (4)
The error correcting code ECCBCA 206 (C0,0–C3,3) is a parity for correcting errors of the BCA information data IBCA 202 and the error detecting code EDCBCA 204 and is expressed as the remainder obtained by dividing input data IBCAj(x) by a polynomial GpBCA(x) as shown in the following equations (5)–(9). A byte operation is expressed using a capital letter ‘X’.
                                          R            BCAj                    ⁡                      (            X            )                          =                              ∑                          i              =              0                        3                    ⁢                                    C                              j                ,                i                                      ·                          X                              3                -                i                                                                        (        5        )                                                      D            BCAj                    ⁡                      (            X            )                          =                                            ∑                              i                =                0                                                              4                  ⁢                  n                                -                2                                      ⁢                                          I                                  j                  +                                      4                    ⁢                    i                                                              ·                              X                                  51                  -                  i                                                              +                                    ED              j                        ·                          X                              52                -                                  4                  ⁢                  n                                                                                        (        6        )            ECCBCAj(X)=IBCAj(X)modGpBCA(X)  (7)
                                          G            pBCA                    ⁡                      (            X            )                          =                              ∏                          k              =              0                        3                    ⁢                                          ⁢                      (                          X              +                              a                k                                      )                                              (        8        )            Gp(x)=x8+x4+x3+x2+1  (9)
On the other hand, as shown in the BCA code structure of FIG. 2, there is a re-synchronizing byte RSBCA1 area which is not used in the BCA code area. That is, the BCA code is written in the BCA code area provided, for example, near a lead-in area of the disk and there is an unused re-synchronizing byte area in the BCA code area. The lead-in area may be defined so as to include a separate area as the BCA code area.
A conventional method for discriminating the type of a disk used in the DVD player will now be described. If the user inserts the DVD-series or CD-series disk into the DVD player and a tray is closed, the DVD player sets its operating mode to a CD mode and starts focus searching. During the focus searching, the DVD player checks whether there is a focus error. If two focus error signals are respectively generated in the up and down movement directions of a lens, the DVD player judges the inserted disk to be a dual layer disk. If one focus error signal is generated, the inserted disk is regarded as a single layer disk. If focusing has ended, the DVD player rotates a spindle motor and checks a phase difference between E and F signals detected by an E/F photo diode of an optical pickup. If the phase difference is 180°, the inserted disk is judged to be the CD-series disk, and if there is no phase difference, it is regarded as the DVD-series disk. Thereafter, the DVD player checks a lead-in area of the disk to distinguish a V-CD (video CD), a CD-audio from the CD-series disk, and DVD-single, DVD-dual from the DVD-series disk. Thus, the disk discriminating operation is completed. This operation is controlled by a microcomputer which is a main controller of the DVD player.
Meanwhile, since the above-described disk discriminating operation is performed step by step, the microcomputer passes through many steps for detecting the type of disk. Therefore, the load on the microcomputer increases, and it takes a lot of time to discriminate the type of the disk. If the disk discriminating process has not ended in a short time period, a waiting time until a normal playback state is performed may be very long. Moreover, a check as to whether the disk is a dual layer or a single layer is made by using the focus error signal, and a determination as to whether the disk is the CD-series or the DVD-series is made from the phase difference between the E and F signals by utilizing the fact that a track pitch of the CD-series disk is different from that of the DVD-series disk. Therefore, if the disk has scratches, the disk player may wrongly detect the type of the disk. When considering future optical disks which will be put on the market, it becomes very difficult to discriminate the type of the disk and there will be a strong possibility that the type of the disk will be wrongly detected.